In the installation of a prosthetic shoulder joint into a patient's body, a glenoid component is implanted into the glenoid vault of the patient's scapula. An obverse surface of the glenoid component is configured for articulating contact with a humeral component carried by the patient's humerus. A reverse surface of the glenoid component is secured to the bone surface of the glenoid vault.
Because the shoulder prosthesis is normally provided to correct a congenital or acquired defect of the native shoulder joint, the glenoid vault or surface often exhibits a pathologic, nonstandard anatomic configuration. A surgeon must compensate for such pathologic glenoid vault anatomy when implanting the glenoid component in striving to achieve a solid anchoring of the glenoid component into the glenoid vault. Detailed preoperative planning, using two- or three-dimensional internal images of the shoulder joint, often assists the surgeon in compensating for the patient's anatomical limitations. During the surgery, one or more elongated pins may be inserted into the surface of the patient's bone, at a predetermined trajectory and location, to act as a passive landmark or active guiding structure in carrying out the preoperatively planned implantation. These “guide pins” may remain as a portion of the implanted prosthetic joint or may be removed before the surgery is concluded. This type of pin-guided installation may be used with any joint replacement procedure—indeed, in any type of surgical procedure in which a surgeon-placed fixed landmark is desirable. For example, a hip replacement procedure may use a guide pin to facilitate installation of an acetabular prosthetic component into a pelvis in a similar manner to that described above for a shoulder replacement component. As another example, a guide pin could be placed in either a bony or “soft” patient tissue to serve as a substantially fixed landmark for any surgical reason and in any desirable patient tissue.
In addition, and again in any type of surgical procedure, modern minimally invasive surgical techniques may dictate that only a small portion of the bone or other tissue surface being operated upon is visible to the surgeon. Depending upon the patient's particular anatomy, the surgeon may not be able to precisely determine the location of the exposed area relative to the remaining, obscured portions of the bone through mere visual observation. Again, a guide pin may be temporarily or permanently placed into the exposed bone surface to help orient the surgeon and thereby enhance the accuracy and efficiency of the surgical procedure.
A carefully placed guide pin, regardless of the reason provided, will reduce the need for intraoperative imaging in most surgical procedures and should result in decreased operative time and increased positional accuracy, all of which are desirable in striving toward a positive patient outcome. Accordingly, a surgeon may be provided with an adjustable tool to dictate at least one of the insertion location and the insertion trajectory for the inserted guide pin, as desired by the surgeon and/or as predetermined through pre-operative or intraoperative planning. A suitable adjustable tool is disclosed in co-pending U.S. patent application Ser. No. 12/854,362, filed 11 Aug. 2010 and titled “Method and Apparatus for Insertion of an Elongate Pin into a Surface”, which is incorporated herein by reference in its entirety and will be referenced as an example of an adjustable tool throughout this description. It will often be desirable for the adjustable tool to be “set” with the insertion location and/or insertion trajectory before or during the surgery, to minimize the time needed for placement of the pin.